The present invention relates to a heating roller for fixing toner in especially an electrophotographic apparatus such as a printer.
Conventionally, toner fixing device in an electrophotographic apparatus such as a printer is constituted such that a heating roller having a heating means, and a press roller located to face each other, and printed paper is allowed to pass between these rollers so that toner is heated and fixed.
Moreover, as for the above-mentioned heating roller, a heating roller, which is constituted such that a heating element such as a halogen lamp is provided into a metallic pipe which is made of aluminum or stainless steel, etc, has been used, but there arose a problem that it needed not less than one minute for warming up because of its low heat effectiveness, and its electric power consumption also became high.
Therefore, there suggests a heating roller which is constituted such that a heating resistor is provided onto the outer circumferential surface of a cylinder made of a metallic pipe with an insulating layer made of an organic resin such as polyimide lying therebetween, and a cleavage layer is provided onto its surface (cf. Japanese Patent Application Laid-Opens No.55-72390/1980 and No.62-200380/1987, etc).
In addition, there also suggests a heating roller for fixing which is constituted such that a heating resistor is provided onto the inner circumferential surface of a cylinder with an insulating layer lying therebetween, and a cleavage layer is provided onto the outer circumferential surface of the cylinder (cf. Japanese Patent Application Laid-Open No.55-72390/1980, etc).
However, in the case of such a heating roller for fixing constituted such that a heating resistor is provided onto the circumferential surface of the cylinder with the insulating layer lying therebetween, during a long time use, there arose a problem that the cylinder and the heating resistor were easily short-circuited because of poor insulation of the insulating layer.
In the present invention, therefore, a heating roller for fixing, which is constituted such that a heating resistor is provided onto the circumferential surface of the cylinder with the insulating layer lying therebetween, and a cleavage layer is provided onto the outermost circumferential surface, is characterized in that the maximum height of surface roughness (Rmax) on the surface of the heating resistor of the cylinder is in the range of 0.8 to 50 .mu.m.
Furthermore, the present invention is characterized in that no protrusion whose height exceeds 50 .mu.m exists on the surface of the cylinder, and a number of the protrusions whose height is 20 to 50 .mu.m is less than 2 per 1 cm.sup.2, and a number of the protrusions whose height is 10 to 20 .mu.m is less than 5 per 1 cm.sup.2.
Namely, since the above-mentioned cylinder is mostly formed by drawing and converting a metallic pipe, many protrusions exist on its surface, and its maximum height of surface roughness(Rmax) is about 70 to 130 .mu.m. For this reason, the thickness of the insulating layer becomes thinner at the protruded portions, and it easily causes poor insulation. In the present invention, accordingly, it was found that poor insulation could be prevented by removing the protrusions which exist on the surface of the above-mentioned cylinder, so that the maximum height of surface roughness(Rmax) is in the range of 0.8 to 50 .mu.m.
In addition, even if the maximum height is within the said range, a lot of protrusions easily cause poor insulation. So, in this invention, it was found that when poor insulation can be further pretended by means that no protrusion whose height exceeds 50 .mu.m exists on the surface of the said cylinder, and a number of the protrusion whose height is 20 to 50 .mu.m is less than 2 per 1 cm.sup.2, and a number of the protrusion whose height is 10 to 20 .mu.m is less than 5 per 1 cm.sup.2.
The present invention relates to a heating roller for fixing toner in especially an electrophotographic apparatus such as a printer, and relates to a cylindrical heater which is used as a heater for hot water, and a air-conditioning heater.
Conventionally, a toner fixing device in the electrophotographic apparatus such as a printer is constituted such that a heating roller having a heat means, and a press roller located to face each other, and a printed paper is allowed to pass between these rollers so that toner is heated and fixed.
Moreover, as for the above-mentioned heating roller, a heating roller, which is constituted such that a heating element such as a halogen lamp is provided into a metallic pipe made of aluminum or stainless steel, etc, but there arose a problem that it needed not less than one minute for warming up because of its low heat effectiveness, and its electric power consumption also became high.
Therefore, there suggests a heating roller which is constituted such that a heating resistor is provided onto the outer circumferential surface of the cylinder made of a metallic pipe with an insulating layer made of an organic resin such as polyimide lying therebetween, and a cleavage layer is provided onto its surface (cf. Japanese Patent Application Laid-Opens No.55-72390/1980 and No.62-200380/1987, etc).
As shown in FIG. 11, there also suggests a heating roller which is constituted such that a spiral slots 131 are formed on the full length of the heating resistor 103 which is formed on the whole surface of the cylinder 101 (cf. Japanese Patent Application Publication No.6-36121/1994 and Japanese Patent Application Laid-Open No.2-308291/1990). In this way, a resistance value of the heating resistor 103 is adjusted to be a prescribed value by forming the spiral slots 131, and the resistance value can be partially adjusted by changing intervals between the slots 131. For example, the temperature of both ends of the heating roller for fixing easily drops by its heat radiation, but it is possible to heat uniformly by adjusting the intervals between the slots 131 and raising beforehand its resistance value of both ends of the heating resistor 103.
Furthermore, a cylindrical heater having the same construction as the above-mentioned heater is used as a heater for hot water which heats water running inside, an air-conditioning heater, and a heater for heating a element, etc.
However, in the heating roller for fixing shown in FIG. 11, it is difficult to accurately adjust its resistance value partially because the spiral slots 131 are shaped on the full length thereof.
Namely, in the heating roller for fixing, since heat radiation easily occurs on its ends as mentioned above, it needs to raise the resistance of its ends. Furthermore, it needs to adjust the heat value by delicately changing the resistance value along an axial direction of the cylinder like that it needs to vary the heat value on a paper-passing part from that on the other part. On the other hand, in the spiral slots 131 shown in FIG. 11 extending to the full length thereof, it is very difficult to accurately form the slots 131 by delicately changing its interval since the resistance value can be adjusted only by the intervals of the slots 131.
Accordingly, the present invention provides a cylindrical heater having a heating resistor on a surface of the cylinder with an insulating layer lying therebetween is characterized in that the heating resistor is divided into plural zones along an axial direction of the cylinder, and slots for adjusting the resistance are respectively shaped in each zone.
Namely, the slots are not formed on the full length of the surface, the slots are formed respectively in each zone along an axial direction. As a result, the resistance value can be adjusted partially and easily.
In addition, the present invention is characterized in that the slots formed almost parallel at a certain angle with respect to the axial direction of the cylinder. Furthermore, the almost parallel slots mean that respective slots are arranged almost parallel when the heating resistor is unfolded in plain style.
In addition, the present invention is characterized in that the slots are composed of slots extended along the axial direction of the cylinder and branch slots connected thereto.
The present invention relates to a heating roller for fixing toner in especially an electrophotographic apparatus such as a printer, and relates to a cylindrical heater which is used as a heater for hot water and an air-conditioning heater.
Conventionally, a toner fixing device in the electrophotographic apparatus like as a printer is constituted such that a heating roller for fixing having a heat means, and a press roller located to face each other, and a printed paper is allowed to pass between these rollers so that toner is heated and fixed.
Moreover, as for the above-mentioned heating roller, a heating roller, in which a heating element such as a halogen lamp is provided into a metallic pipe made of aluminum or stainless steel, etc, has been used but there arose a problem that it needed not less than one minute for warming up because of its low heat effectiveness, and its electric power consumption also became high.
Therefore, as shown in FIG. 18, there suggests a heating roller for fixing which is constituted such that a heating resistor 203 coated with nickel or the like is formed on the outer circumferential surface of a cylinder 201 composed of a metallic pipe with an insulating layer 202 made of glass, ceramics, and resin or the like lying therebetween, and the ring-shaped electrode member 205 is located on its both ends, and the rest of the heating resistor 203 is covered by a cleavage layer 206 (cf. Japanese Patent Application Laid-Opens No.62-200379/1987 and No.58-40571/1983). In this heating roller for fixing, while spinning the cylinder 201, a load dispatching member (not shown) is brought into contact with the outer circumferential surface of the electrode members 205 on both ends, and while being scraped, power is fed, so it is possible to energize and heat the heating resistor 203.
Moreover, there is a heater for hot water constituted such that a ceramic heater is put onto the outer circumference of a stainless steel pipe to heat the water running inside the pipe, and it is also used as an air-conditioning heater and a heater for heating an element or the like having the same construction.
However, in the heating roller for fixing shown in FIG. 18, there arose a problem that heat radiation easily occurs since the heating resistor 203 is located on the outer circumferential surface of the cylinder 201, and the cylinder 201 is hollow. Therefore, there were some inconveniences that it is impossible to heat uniformly by heat radiation on its ends, and its electric consumption becomes high because of its great heating loss.
Moreover, since the electrode members 205 were located on the outer surface, when using in fixing apparatus, there arose another problems that some noises occur by catching toner, and the electrode members 205 are easily deteriorated by water vapor, chlorine gas, etc, generated from the paper.
Therefore, the present invention provides a cylindrical heater, which is constituted such that a heating resistor is provided onto the inner surface thereof, and electrode members connected to the heating resistor is provided onto both ends of the inner side of the cylinder, is characterized in that electrode member stops up a hollow of the cylinder.
Furthermore, the present invention provides a cylindrical heater which is characterized in that a load dispatching member for supplying power feeds a power while being scraped on the electrode member, and a ratio L/D of a distance L of between a scrape surface and an end surface to an inner diameter D of the cylinder, is not more than 0.6.
By means of the present invention, it is possible to prevent from the heat radiation, to heat uniformly, and to reduce the heat loss and save the electric power by forming the heating resistor on the inner surface of the cylinder and by forming the electrode member to stop up a hollow thereof.
Furthermore, since the electrode member is provided into the cylinder, it is possible to prevent toner from being caught and the corrosion due to water vapor or chlorine gas when using as the heating roller for fixing.